Abnormalities in Body Shape

PHOTO

Anterior end of Glossodoris hikuerensis from Kwajalein, Marshall Islands, showing three rhinophores. See Scott Johnson's message. PHOTO: Jeanette Johnson.

Through developmental mistakes and after damage, animals sometimes grow a weird structure somewhere on their bodies.

Here is a list of relevant messages which are either attached below or elsewhere in the Forum.

Authorship details
Rudman, W.B., 2000 (January 28) Abnormalities in Body Shape. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/abnormal

Related messages


Chromodoris leopardus with a hood

May 18, 2002
From: Erwin Köhler

Dear Bill,
Attached is a shot of a Chromodoris leopardus with a 'hood'. It was made by Linda Cline email lscline@dancing-fish.com at the Solomon Islands, wreck of the 'Ann', 04 Nov 2000 - size and depth are not recorded.

Erwin

Erwin@medslugs.de

Köhler, E., 2002 (May 18) Chromodoris leopardus with a hood. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6898

Thanks Erwin,
When I saw this photo it reminded me of an earlier message. Have a look at Mary Jane's photo, which from the data, is almost certainly the same animal.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (May 18). Comment on Chromodoris leopardus with a hood by Erwin Köhler. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6898

Damaged Chromodoris tinctoria f rom Malaysia

July 9, 2001
From: Asther M. Lau

Hi again,

Recently I found a Chromodoris tinctoria at Sea Fan Garden, Tioman, Malaysia.

What puzzles me was the scar that it has on its body. It looked as if it's been torn nearly half its body across and now, instead of having a whole nice body, there is a huge scar on its right side near its head. (if you look from the top). My question is, is there a possibility that this creature could have been bitten and then managed to heal, leaving such a nasty scar on it?

It was about 4cm long. And looked pretty healthy then. What animals could have this beautiful thing for food?

Thank you for your time.
Asther

diveworldwide@yahoo.com

Lau, A.M., 2001 (Jul 9) Damaged Chromodoris tinctoria f rom Malaysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4751

Dear Asther,
It has possibly been bitten by a fish which then spat it out because it tasted bad. Often animals with bright colours also have distasteful glands in their skin so that potential predators learn to leave these bright colour patterns alone. Have a look at the page on Colour & defence for some background information.

I have started a page to record predation observations because there is very little known about what actually eats nudibranchs. Also have a look at the page on Abnormalities where there are links to photos of abnormal body shapes. Some of these are apparently caused by developmental mistakes when the animal was growing, but others are almost certainly the reult of regrowth after predation damage.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jul 9). Comment on Damaged Chromodoris tinctoria f rom Malaysia by Asther M. Lau. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4751

Chromodoris leopardus freak

January 10, 2001
From: Mary Jane Adams

Hi Bill,
Here is one for your abnormal file. I found this Chromodoris leopardus sitting on the Wreck of the Ann in the Russell Group of the Solomon Islands. At first I thought it didn't have any rhinophores. However, when I looked at my slides I saw them peeking out between two flaps at the head end of the mantle. Another diver shot video of this beast a little later when it was crawling and flapping it's mantle. It showed the rhinophores rotating into the usual vertical position when the mantle was lifted. They looked normal as did the single mouth which was located beneath the lower mantle skirt.
Depth: 10 meters
Length: 4 cm
November 4, 2000
Best regards,
Mary Jane

divepng@yahoo.com

Adams, M.J., 2001 (Jan 10) Chromodoris leopardus freak. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3482

Dear Mary Jane,
A very interesting find. Through some developmental accident it has grown two anterior mantle flaps! Must be difficult for it to know what to do with the rhinophores.
Bill Rudman.

Missing in action

June 27, 2000
From: Mary Jane Adams


Dear Bill,

I have several photos in my files of nudibranchs with only one rhinophore and I am very curious about them. Has anyone actually observed fish biting them off? Do they regenerate? I have heard that fish generally avoid eating nudibranchs because they taste very bitter. Is it known if fish can detect the bad taste by smelling them? Could some of the missing rhinophores be the result of developmental a defect? I have no photos of branchs with both rhinophores missing. Could they survive if both were bitten off?

UPPER: Ceratosoma tenue on silty sand, 5 meters deep, Alotau, Papua New Guinea, May 22. 1998
LOWER: Glossodoris cincta in a sandy slope, Normanby Island, Papua New Guinea, May 24, 2000

Thanks!
Mary Jane

mjadams@earthlink.net

Adams, M.J., 2000 (Jun 27) Missing in action. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2530

Dear Mary Jane,
When you find an opisthobranch with a bit missing it can have occurred in three ways.

•Injury. This is usually caused by the bite of a predator. Have a look at the Opisthobranch Defence page for some background information. Although many sea slugs have glands and sacs in their skin filled with distasteful chemicals, they only deter predators who know about them. So some sea slugs do get bitten by inexperienced predators. Often the distasteful chemicals cause the predator to spit the slug out, and usually the slugs seem able to withstand quite a bit of damage. In Ceratosoma the dorsal horn (see arrow) contains the distasteful chemicals. It is usually brightly coloured, and I have suggested in the past that it may act as a lure attracting fish to the nastiest part of the body. In the photo alongside is a Ceratosoma tenue from Tanzania with this horn apparently bitten off. The animal was apparently quite healthy, so perhaps it is a useful defence mechanism.

•Autotomy. Some nudibranchs are able to break off sections of their body as a defensive strategy, just like some lizards can lose their tails. each species has a particular 'bit' that is broken off. There are some examples on the Autotomy page.

• Developmental Error. In an earlier message you sent a photo of Chromodoris tinctoria with a funny tube on its mantle. This was clearly a developmental error. I think in both the photos here there is some developmental error as in neither case can I see any sign of the rhinophore pocket into which a 'bitten off' rhinophore normally be able to withdraw. Strangely aberrations with rhinophores seem to occur quite often. Usually it involves fusing of the two, as in Scott Johnson's photo of Gymnodoris ceylonica, but I guess absence is also possible.

Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Jun 27). Comment on Missing in action by Mary Jane Adams. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2530